Ambient condition detectors have been found to be useful in providing an indication of the presence or absence of the respective condition being detected. Smoke, gas, temperature, and relative humidity detectors, for example, have been found useful in providing early warnings of the presence of mechanical malfunction and/or fire.
When used in Heating/Ventilation/Air-conditioning (HVAC) duct systems, ambient condition detectors are able to not only signal the presence of alarm conditions anywhere in the building, but also in the machinery of the HVAC ducts themselves. Generally, detectors are placed in either the air-intake or return. When detectors are desired in both intake and return ducts, however, two separate units are installed in each individual duct. This method results in redundant use of circuitry which also adds to the cost of installation and service.
Therefore, there continues to be a need for solutions to monitor ambient air conditions in both air supply and air return ducts reducing redundant use of control or monitoring circuitry. It is also desirable to provide an air flow detection system and method that is able to sample the air flow through the detector and compare it to ambient air flow conditions and thereby signal restriction in air flow.